(a) Field of the Invention
The present invention relates to a liquid crystal display and a thin film transistor array panel usable therefore the liquid crystal display.
(b) Description of the Related Art
A liquid crystal display (LCD) is a widely used type of flat panel display. An LCD includes a liquid crystal (LC) layer interposed between a pair of panels provided with field-generating electrodes. The LC layer is subject to an electric field generated by the electrodes, and variations in the field strength change the molecular orientation of the LC layer. A change in the molecular orientation of the LC layer, in turn, changes the polarization of light passing through the LC layer. Light transmittance through the LC layer is changeable not only by controlling the strength of the electric field in the LC layer but also by using polarizer(s). Appropriately disposed polarizer(s) change light transmittance through the LC layer by affecting the polarization of light.
One measure of LCD quality is a viewing angle, which is defined by the angle from the perspective of a viewer where the LCD exhibits a predetermined contrast ratio. Various techniques for enlarging the viewing angle have been suggested, including utilizing a vertically aligned LC layer and providing cutouts or protrusions at the field-generating electrodes such as pixel electrodes and a common electrode.
Although using cutouts or protrusions with a vertically aligned LC layer does achieve the desired enlargement of the viewing angle, it also has a negative effect on the display quality in that cutouts and the protrusions reduce the transmittance. To compensate for the decrease in transmittance, it has been suggested that the size of the pixel electrodes be increased. However, an increase in the size of the pixel electrodes results in a closer distance between the pixel electrodes, which causes strong lateral electric fields between the pixel electrodes. Strong electric fields between pixel electrodes can be problematic as they cause unwanted altering of the orientation of the LC molecules, creating textures and light leakage and deteriorating display characteristics. Although the textures and the light leakage may be screened by a wide black matrix, using a wide black matrix also reduces the aperture ratio.
In addition to creating undesirable lateral inter-pixel electric fields, an increase in the size of the pixel electrodes may raise the parasitic capacitance between the pixel electrodes and the data lines. When an active area on a backplane for an LCD is too large to use an exposure mask, the entire exposure is accomplished by repeating a divisional exposure called step-and-repeat process. One divisional exposure unit or area is called a shot. Since transition, rotation, distortion, and etc. are generated during light exposure, the shots are not aligned accurately. Accordingly, the parasitic capacitances generated between signal lines and pixel electrodes differ depending on the shots, and this causes a luminance difference between the shots. This difference in luminance is recognized at the pixels located at a boundary between the shots, generating a stitch defect on the LCD screen.
In addition to the above problems associated with enlarged pixel electrodes, there is also the issue of a parasitic capacitance between the data lines and the common electrode that may cause disorder of liquid crystal molecules.
A method of enlarging the viewing angle without the aforementioned problems is desired.